Things to Know




#Prokaryote Nutrition




#Prokaryote Reproduction




Horizontal Gene Transfer

Prokaryotes: The big picture

  • ‘Prokaryotes’ are not a monopheyltic group
    • Kingdoms Bacteria & Archaea; each with unique traits
    • most species diverse groups on Earth


  • Diversity of ways of making a living
    • sources of energy to make ATP
    • sources to produce carbon
      • hetrotrophs
      • autotrophs (light, chemical)


  • Co-evolution with the planet and other organisms
    • oxygen poor to oxygen rich world
    • extremeophiles (temperature, pH, salt,etc.)
    • prokaryotes are most abundant organisms on Earth!

Prokaryote functional diversity

  • Sources of carbon
    • autotrophs produce organic molecules themselves
      • chemically through oxidation of inorganic molecules
      • utilize light energy & inorganic molecules
    • heterotrophs obtain organic molecules from environment


  • Energy for ATP (without mitochondria)
    • aerobic respiration= electron transport chain uses O2
    • anaerobic respiration = electron transport chain does not use O2
    • fermentation = breakdown of sugar directly
    • via photosynthesis
    • directly from inorganic molucules


Picture: Iron-oxidizing bacteria derive ATP by oxidizing ferrous iron to power the electron transport chain

Prokaryotes need nitrogen and may need oxygen

  • Metabolism varies with respect to oxygen (reflects deep evolutionary history)
    • required for cellular respiration for some
    • harmed or killed by O2 for others
    • some can adjust based on presence/absence of O2


  • Nitrogen is essential for production of amino acids
    • prokaryotes less limited in obtaining nitrogen compared to other organisms


  • Some bacteria convert atmospheric nitrogen (N2) into usable forms
    • termed Nitrogen fixation


  • Picture: Bacteria work together
    • photosynthesis and N fixation

Metabolic cooperation by bacteria can lead to Biofilms


Biofilms are living communities that allows microorganisms (such as single-celled bacteria) to behave as a group


  • Fossil evidence of biofilms dates to about 3.25 billion years ago


  • More than 75% of human infections are thought to be related to the presence of microorganisms in the form of biofilms
    • on the surface of tissues or medical devices
    • dental plaque!


  • Biofilms are not exclusive to prokaryotes but include them
    • green film on pond rocks

Rapid reproduction contributes to genetic diversity via mutations

  • Rapid reproduction and large populations leads to many mutations
    • diversity NOT created through sexual reproduction
    • 2 x 10^10 new E.coli cells in human intestine each day
    • possible for millions of mutations each day


  • Example: Infant microbiome diversifies rapidly
    • colonization happens right after birth
      • parent, milk, skin, environment
    • selection pressures are strong
      • developing immune shifts
      • diets shifts
      • antibiotics, illnesses, etc.
    • community is unstable
      • mutations/new traits can spread fast
      • horizontal gene transfer

Reproduction in prokaryotes: Binary fision


  • Asexual: daughter cells identical to parent
    • rapid reproduction via mitosis
    • not great for genetic diversity
      • no mixing of DNA from parents
      • no meiosis to shuffle genes


  • Mutations add to diversity but are still rare


  • Horizontal gene transfer does increases genetic diversity:
    • transformation =
    • transduction =
    • conjugation =

Genetic Recombination: Bacterial Transformation

Utilizing transformation for science advancement…

  • Manipulating DNA sequences in vitro, creates recombinant DNA molecules that have new combinations of genetic material


  • Recombinant DNA is then introduced into a host organism
    • If the DNA comes from a different species, the host organism is considered to be transgenic.

Genetic Recombination: Bacterial Conjugation

Donor cell attaches to recipient via pilus (bridge) and transfers plasmids or chromosomal DNA (less common). Does not have to be same species or even genera!!!

Many R plasmids carry genes for antibiotic resisitance



  • Many species of bacteria carry genes that code for enzymes that destroy/hinder antibiotics
    • tetracycline, ampicillin


  • Genes often carried in plasmids (R plasmids)


  • R plasmids have genes that encode for pili (conjugation bridge)
    • enable conjugation
    • resistance genes can spread quickly

Prokaryotes are incredible diverse

  • >20,000 described but > millions estimated


  • Genomes are super diverse because of horizontal gene transfer


  • Bacteria are the most commonly known prokaryotic species
    • from pathogens to yogurt


  • Archaea: share traits with bacteria and eukaryotes
    • earliest ancestors in extreme environments
    • important for environmental methane production

Prokaryotes matter: Cyanobacteria


  • Cyanobacteria: first evidence ~3.5 bya
    • blue-green algae
    • aquatic and photosynthetic
    • use chlorophyll (pigment that absorbs light)


  • Photosynthesis evolved independently in other bacterial groups
    • molecular mechanisms, pigments and oxygen conditions differ
    • cyanobacteria are a monophyletic group (oxygenic photosynthesis)


  • Eukaryotes acquired photosynthesis by engulfing cyanobacteria!

Prokaryotes matter: Great Oxygenation by Cyanobacteria

Banded iron formation (2.4 bya) the result of oxygen, dissolved iron and sea water

Prokaryotes matter: Oxygen revolution

Prokaryotes matter: Chemical Recycling in Nature

Prokaryotes matter: Species Interactions

Prokaryotes matter: Microbiomes in Animals

Helps with digestion, destroys harmful bacteria and helps control your immune system.

Prokaryotes matters: Humans